Unresponsive after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 216 reports of unresponsive in dogs after Ivermectin + Pyrantel. That is 0.1% of all reports for this medicine, compared with 0.4% across reports for all dog medicines, so it is reported less often than average with this medicine.

216Reports

65%Marked serious

26%Recovered

25%Died or euthanised

7 daysTypical onset

How soon it started

Same day

26 23%

1–2 days

19 17%

3–7 days

12 11%

1–4 weeks

13 12%

Over a month

43 38%

How the animals did

Recovered

54 25%

Recovered with lasting effects

3 1.4%

Still unwell when reported

17 7.9%

Died

27 13%

Euthanised

28 13%

Not known

87 40%

Problems reported at the same time

76 35%

59 27%

55 25%

48 22%

37 17%

34 16%

27 13%

23 11%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Ivermectin prevents heartworm disease (monthly). Pyrantel treats roundworms and hookworms.

Products with this combination include Heartgard Plus, Tri-Heart Plus, Iverhart Plus. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Some herding breeds (for example Collies) carry the MDR1 gene variant and can be more sensitive to this drug class at high doses.

Questions owners ask

Can Ivermectin + Pyrantel cause unresponsive in dogs?: 216 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
How soon after a dose was it reported?: In half of the reports with dates, it started within 7 days of the first dose.
What should I do?: Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Unresponsive with similar medicines

Unresponsive after Milbemycin Oxime + Spinosad (Trifexis) 331 reports · 0.3% of its reports
Unresponsive after Moxidectin (ProHeart 6) 266 reports · 0.5% of its reports
Unresponsive after Milbemycin Oxime + Praziquantel (Interceptor Plus) 77 reports · 0.2% of its reports
Unresponsive after Milbemycin Oxime (Interceptor) 59 reports · 0.2% of its reports
Unresponsive after Selamectin (Revolution) 57 reports · 0.2% of its reports
Unresponsive after Ivermectin (Heartgard) 128 reports · 1.1% of its reports
Unresponsive after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 21 reports · 0.2% of its reports

All reported side effects of Ivermectin + Pyrantel in dogs · Medicines most reported with unresponsive